Letters: Fat philosophy; survival of the cutest

From Paul GrayI read Jon White's story on the dietary role of fat with a mixture of despair and amusement (2 August, p 32).

In the 1980s, I spent 10 years of my career at the European Commission in charge of food, refocusing legislation on safety and consumer information – such as nutrition labelling – only later to see the obesity epidemic inflate both waistlines and healthcare expenditure. Hence the despair.

Even with simplified presentations such as traffic light labelling – with green indicating that a food contains healthy levels of a nutrient, red the opposite – we should not have expected a public indoctrinated with simplistic concepts, such as the idea that "natural" must be "good", to eat more sensibly.

It is hard enough to scientifically tease out the effect of specific nutrients on health from the complexities of food epidemiology and the variability of human beings, but it is much harder still to use what we know to persuade consumers to improve their health.

Perhaps the doctrine of Paracelsus that underlies all food toxicology, "only the dose makes the poison", should be applied to nutrition. But how to persuade the consumer to take the right dose? Until we have figured it out, is more nutrition research really worthwhile?Alcester, Warwickshire, UK

From Paul TavenerResearch into the effects of dietary fat on disease has suffered from 40 years of distortion and misinterpretation. The establishment of an early consensus on very flimsy evidence, driven by very forceful personalities, has proved disastrous.

Take one example, the Multiple Risk Factor Intervention Trial (MRFIT), which involved over 12,000 middle-aged American men with high cholesterol. Half received treatment for hypertension, intensive counselling to quit smoking, and advice on changing their diet to lower cholesterol. The other half were told to address their health problems however they desired.

After seven years, the trial reported that mortality rates between the two groups were not significantly different.

The MRFIT results should have acted as a wake-up call, but because they did not fit with the by-then-established dogma, they were explained away by various means and quietly forgotten.

The history of research in this area is littered with poor science, muddled thinking and confusion, which is still with us today.Waterlooville, Hampshire, UK

From Jonathan WallaceTim Vernimmen raises some important questions about how we should allocate conservation resources and which species we should save (19 July, p 38).

The broad thrust of his article is that we could focus on the ecosystems or species with the greatest phylogenetic diversity – put simply, those that are most genetically and behaviourally distinct. I agree this is very important, but other factors should not be ignored.

Keystone species such as the sea otter may not qualify in terms of phylogenetic distinction but their significant ecological influence must make them important targets for conservation action.

Likewise, charismatic megafauna such as tigers may get a low score for phylogenetic diversity, but their conservation will benefit a host of other species sharing their habitat, while they act as effective poster species for fundraising efforts.

Finally, it is important that conservationists take full account of the likelihood of success in deciding which species to adopt. If a creature has slipped far down the slope towards extinction, trying to save it would not be justified.Newcastle upon Tyne, UK

From Rafael SantosAndy Extance draws attention to an important alternative to conventional geological storage of carbon dioxide, namely in-situ mineral carbonation (19 July, p 30). The idea is that reacting the dissolved gas with alkaline minerals deep within the Earth's crust allows the carbon to be more safely and permanently stored.

Another alternative is ex-situ mineral carbonation. In this case, alkaline minerals such as olivine and serpentine are mined and milled, then mixed with CO2 in reactors above ground.

The processing costs are inherently higher, but a major benefit is the production of valuable by-products that can be supplied to the construction industry to pay for the process.Leuven, Belgium

From Steven FowkesAndy Coghlan's informative and timely article reported that the anti-arthritis drug etanercept showed promise in halting Alzheimer's disease when injected into the bloodstream (19 July, p 10). But he failed to mention years of clinical, off-label use of the same drug for Alzheimer's, administered by injecting it into the spine.

A decade ago, reports of a reversal in Alzheimer's symptoms began appearing online, and journals have published case reports of this too. Some of the clinical outcomes have been exciting (Journal of Neuroinflammation, DOI: 10.1186/1742-2094-5-2).

Etanercept is a huge molecule and does not cross the blood-brain barrier. It would appear that injecting etanercept directly into the base of the brain might be necessary for delivering the maximum therapeutic effect in cases of Alzheimer's.Cupertino, California, US

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